Thermal insulating foamed material having carbon dioxide adsorbents and method for manufacturing the same

ABSTRACT

A thermal insulating foamed material is a polyurethane foam having closed cells, and produced by mixing, agitating and foaming a polyol, a polyisocyanate, a foam stabilizer, a catalyst, a blowing agent and a carbon dioxide adsorbent. The carbon dioxide adsorbent is produced by mixing and granulating powders of at least one member of alkali metal hydroxides and alkaline-earth metal hydroxides and organic or inorganic powders having a water absorbing property and soaked with water in advance, and formed by a resin film, such as a methacrylic acid ester, which is permeable to carbon dioxide but hardly permeable to water.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of copending application Ser. No.08/599,451, filed Jan. 22, 1996, entitled Thermal Insulating FoamedMaterial Having Carbon Dioxide Adsorbents and Method for Manufacturingthe Same. The entire disclosure of application Ser. No. 08/599,451 asfiled is incorporated herein by reference.

FIELD OF THE INVENTION AND RELATED ART STATEMENT

1. Field of the Invention

The present invention relates to a thermal insulating foamed materialhaving carbon dioxide adsorbents and being for use in refrigerators,freezers and the like, and a method for manufacturing the thermalinsulating foamed material as well as a thermal insulation cabinet usingthe thermal insulating foamed material.

2. Description of the Prior Art

Recent years, in this field there have been needs of decrease in thermalconductivity and improvement in thermal insulation of thermal insulatingfoamed materials from a viewpoint of energy-saving. And, concurrently,the environmental disruption, such as ozone depletion, global warmingand so on by increase of chlorofluorocarbon (hereinafter abbreviated asCFC) and a hydrochlorofluorocarbon (hereinafter abbreviated as HCFC) arebecoming problems. Therefore, in this technical field, it has been veryimportant to meet the above-mentioned needs and to solve these problems.

Accordingly, in the production of rigid polyurethane foam as a typicalthermal insulating foamed material, it has been considered to decreasethe amount of CFC and HCFC to be used, completely removing the ozonedepletion, and to use a blowing agent which is less effective to theglobal warming. Various forming techniques using a hydrocarbon(hereinafter abbreviated as HC), such as pentane or cyclopentane, assuch blowing agent, are now under examination.

In order to improve thermal insulating ability of the rigid polyurethanefoam (hereinafter abbreviated as foam), it is basically important todecrease gaseous thermal conductivity of a gaseous composition in closedcells in the foam. Therefore, it has been considered to be an effectivemeasure to fill the cells in the foam with a gas having a lower gaseousthermal conductivity.

For the purposes of a decrease in the amount of blowing agent to beused, a problem of undesirable solubility between the blowing agent andthe resinous material, and an improvement of properties of the foam suchas a density and so on of the foam, it has been needed to use carbondioxide generated by a reaction of a polyisocyanate and water as ablowing agent for the production of the foam.

However, since carbon dioxide having a high gaseous thermal conductivityremained in cells in the foam containing carbon dioxide as well as theHC as the blowing agent, the thermal insulating ability of a thermalinsulating foamed material was inevitably bad.

As a means of solving these problems, the gazette of the Japaneseunexamined patent application (TOKKAI) sho 57-49628, for example,proposed a method in which carbon dioxide composition was removed bycarbon dioxide adsorbents. In this method, an adsorbent composed ofzeolite and others was mixed in advance into the resinous material, thecarbon dioxide generated by a carbodiimide forming reaction, anisocyanurate forming reaction or the like was adsorbed by the carbondioxide adsorbent and thus cells were filled with HC of a blowing agentalone.

Accordingly, the invention of the manufacturing method using the zeoliteas the above-mentioned carbon dioxide adsorbent, which is disclosed inthe above-mentioned gazette of the Japanese unexamined patentapplication (TOKKAI) sho 57-49628 removes water, which was a primaryfactor for carbon dioxide generation in the isocyanate polymerizationfoam, from the raw material, and carbon dioxide generated during theforming step affording the foam and remained in the cells was removedabsorptively. Thus, in this thermal insulating foamed material, it wasattempted to improve the thermal insulating ability of the foam byremoving the carbon dioxide in the cells. In this invention, the"thermal insulating foamed material" means a foamed substance or matterwhich contains a large number of small foams made by a blowing agent andused to insulate heat.

In the thermal insulating foamed material formed by the above-mentionedconventional manufacturing method JP-A-57-49628, the carbon dioxideadsorbent composed of zeolite and others preferentially adsorbs waterover carbon dioxide. Therefore, water is adsorptively removed uponmixing of the raw materials. This means that there is no ureaformingreaction, a reaction of an organic isocyanate with water, which iseffective for reducing density of the foam to improve the thermalinsulating ability. Accordingly, the thermal insulating foamed materialis formed from a dehydrated material, which results in a formation of ahigh density foam having a deteriorated thermal insulating ability asseen in sole foaming by a blowing agent.

As already discussed cyclopentane is completely free from a possibilityof causing the ozone depletion and has very little effect to the globalwarming. It has hitherto been considered to utilize cyclopentane or thelike as a blowing agent for the thermal insulating foamed material. Thecyclopentane as a composition of the blowing agent, however, is scarcelysoluble in polyetherpolyols which are commonly used materials for rigidpolyurethane foam. Therefore, the amount of cyclopentane to be mixedinto a premix was limited.

Besides, the cyclopentane has a boiling point of 49.3° C., which is veryhigh as compared with 23.8° C. of CF11 or 32.0° C. of HCFC141b, whichare conventionally used blowing agents with a boiling temperature aroundordinary temperature. Therefore, in order to improve the expansion ratioof the foam, increase in the amount of water to be added is essentialfor generating the carbon dioxide as compared with the conventional casein which CFC11 or HCFC141b is used as the blowing agent.

In the prior art method, however, water in the raw material is removedby the carbon dioxide adsorbent upon mixing of the premix. Therefore,there is such an unsolved problem that the expansion ratio of the foamis greatly decreased and that the foam having a low density having highthermal insulating ability can not be produced when cyclopentane in needof water or the like is used as the blowing agent.

It may be considered to use, as the carbon dioxide adsorbent, an alkalimetal hydroxide which has low water absorbing properties and which isexcellent in adsorbing properties for carbon dioxide as compared withzeolite and the like. In this case, however, there is also a problemthat, while the removal of water in the raw material is decreased,adsorbing properties for carbon dioxide can not be effectively exertedafter the forming, i.e. in the foam after water is removed, due to thefact that alkali metal hydroxide exhibits adsorbing properties forcarbon dioxide only in the presence of water.

Accordingly, in this technical field, even if the hydrocarbon etc. isused as the blowing agent, there are yet needs for developing a thermalinsulating foamed material of high quality and excellent in givingthermal insulating ability to the foam, while retaining the expansionratio of a foam as ever.

OBJECT AND SUMMARY OF THE INVENTION

The principal object of the present invention is to solve theabove-mentioned problems and to protect the global environment. Thus,the present invention provides a thermal insulating foamed material ofhigh quality, excellent in thermal insulating ability of the foam asever, while retaining the expansion ratio of the foam, by using avolatile material as the blowing agent, such as a hydrocarbon and thelike completely free from a possibility of causing the ozone depletionand having a very little possibility of causing the global warming. Thepresent invention also provides a method for manufacturing thermalinsulating foamed material and a thermal insulation cabinet using thethermal insulating foamed material.

In order to solve the above-mentioned problems, a thermal insulatingfoamed material in accordance with the present invention comprises afoamed polyurethane resin composition having closed cells, which hastherein carbon dioxide adsorbents formed by at least one member ofcarbonates of alkali metal and carbonates of alkaline-earth metal,covered with resin coating, and has volatile blowing agent in the closedcells.

A thermal insulation cabinet with excellent thermal insulatingproperties is obtained by filling a space formed between a first wallmember and a second wall member with a foamed polyurethane resincomposition, has therein carbon dioxide adsorbents, formed by at leastone member of carbonates of alkali metal and carbonates ofalkaline-earth metal, covered with resin coating, and has volatileblowing agent in closed cells of the foamed polyurethane resincomposition.

A method for manufacturing a thermal insulating foamed material inaccordance with the present invention comprises steps of

producing carbon dioxide adsorbents, which include at least one memberof hydroxides of alkali metal and hydroxides of alkaline-earth metal andwater, and coated with a coating resin film,

mixing the carbon dioxide adsorbents with polyol, catalyst, foamstabilizer, water, volatile blowing agent and polyisocyanate,

producing a foamed polyurethane resin composition having closed cellsincluding carbon dioxide generated by reaction between water andpolyisocyanate, and volatile blowing agent, and

adsorbing the carbon dioxide in the closed cells of the foamedpolyurethane resin composition by the carbon dioxide adsorbents, so asto despite carbonates and substantially fill the cells with the volatileblowing agent.

According to a further aspect of the present invention, themanufacturing method for thermal insulating foamed material uses acarbon dioxide adsorbent produced by mixing and granulating powders ofan alkali metal hydroxide or the like having a lower water absorbingproperties and organic or inorganic materials having a water absorbingproperties and soaked with water in advance, and coating the surface ofthe granulated material with a resin which is permeable to carbondioxide but hardly permeable to water, or a carbon dioxide adsorbentproduced by granulating powders of an alkali metal hydroxide or the likecontaining water, and coating the surface of the granulated materialwith a resin which is permeable to carbon dioxide but hardly permeableto water. Therefore, the carbon dioxide adsorbent does not adsorb waterin the materials.

Accordingly, the expansion ratio of the foam is not decreased andlowering of the density of the foam becomes possible. Further, since thepowders of the alkali metal hydroxide or the like are in a statecontacting with a substance soaked with water or the like, they canexert carbon dioxide adsorbing ability in the foam after losing water.

Furthermore, since the carbon dioxide adsorbent is coated by the resinfilm which is permeable to carbon dioxide but hardly permeable to water,the water carried by the carbon dioxide adsorbent has no effect on thefoaming action and, in addition, there is no fear of diffusing waternewly generated in the course of the reaction of the alkali metalhydroxide absorbing carbon dioxide. Accordingly, the properties of thefoam such as the density or the like are not adversely affected, and thecarbon dioxide in the cells is removed allowing improvement of thermalinsulating properties of the foam.

While the novel features of the invention are set forth particularly inthe appended claims, the invention, both as to organization and content,will be better understood and appreciated, along with other objects andfeatures thereof, from the following detailed description taken inconjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a carbon dioxide adsorbent mentioned inExample 2 of the present invention.

FIG. 2 shows a sectional view of a thermal insulation cabinet mentionedin Example 2 of the present invention.

FIG. 3 shows a sectional view, partly cut away, of a thermal insulationcabinet mentioned in Example 3 of the present invention.

FIG. 4 shows a sectional view of the thermal insulation cabinet directlybefore filling raw materials in Example 3 of the present invention.

FIG. 5 shows a sectional view of the thermal insulation cabinet afterfilling raw materials in Example 3 of the present invention.

It will be recognized that some or all of the Figures are schematicrepresentations for purposes of illustration and do not necessarilydepict the actual relative sizes or locations of the elements shown.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following will be mentioned embodiments of a thermal insulatingfoamed material having carbon dioxide adsorbents, a method formanufacturing said thermal insulating foamed material and a thermalinsulation cabinet having said thermal insulating foamed material of thepresent invention.

The thermal insulating foamed material as will be seen in Example 1 inaccordance with the present invention is rigid polyurethane foam. Therigid polyurethane foam is formed by mixing and agitating apolyisocyanate and a premix composition formed by mixing a polyol, afoam stabilizer, a catalyst, a blowing agent including water and acarbon dioxide adsorbent. The carbon dioxide adsorbent is produced bymixing and granulating at least one member of an alkali metal hydroxideand an alkaline-earth metal hydroxide and organic or inorganic powders,which have a water absorbing property and are soaked with water inadvance, and the surface of the grains of mixture is coated with a resinwhich is permeable to carbon dioxide but hardly permeable to water.Alternatively, the carbon dioxide adsorbent is produced by granulatingpowders of at least one member of an alkali metal hydroxide and analkaline-earth metal hydroxide using an organic or inorganic substancecontaining water as a binder, and coating the surface of the granulatedmaterial with a resin which is permeable to carbon dioxide but hardly topermeable to water.

The organic solution of the resin for coating the surface of the carbondioxide adsorbent is a solution of high molecular substance dissolved inwater or an organic solvent (for example, alcohols such as methanol,ethanol or the like, toluene, xylene, methylene chloride and the like).The high molecular substance includes, for example, polyvinyl alcohol,polyvinyl acetate, polyvinyl pyrrolidone, polyacrylic acid ester,polymethacrylic acid ester, ethyl cellulose, carboxymethyl ethylcellulos and the like. The viscosity of such solution is preferably 500cp or less at a temperature in a granulating step in view of limitationof the wet spray coating in the granulating step. It is preferred thatthe concentration of the solution is about 2-40 wt % from the practicalview point.

The outer dimension of the granulated carbon dioxide adsorbent in therigid polyurethane foam (hereinafter abbreviated as foam) are preferablyfrom 0.2 to 1.0 mm, of which the lower limit is a limit of granulationand the upper limit is a dimension which does not inhibit formation ofcells upon urethane foaming.

The carbon dioxide adsorbent as will be seen in Example 2 in accordancewith the present invention is in the form of grains of mixture producedby mixing and granulating at least one member of an alkali metalhydroxide and an alkaline-earth metal hydroxide and a hydrate ofinorganic compound, for example, a hydrate having a heat of hydration of20 kcal/mol or more. The carbon dioxide adsorbent is formed by coatingthe surface of the granulated material with a resin which is permeableto carbon dioxide but hardly permeable to water. The powders such asalkali metal hydroxide or the like include water, as water in thehydrate, which is essential for adsorbing carbon dioxide, and protectedby the resin coating. Therefore, they can exert an ability of adsorbingcarbon dioxide even in a system free from water. Further, when a hydrateof inorganic compound having a heat of hydration of 20 kcal/mol or moreis mixed, water does not evaporate particularly in a granulating step atthe ordinary temperature. Therefore, the carbon dioxide adsorbentsufficiently exerts an ability of adsorbing carbon dioxide.

A thermal insulating foamed material as well as be seen in Example 3 inaccordance with the present invention is manufactured, in the mixing andagitation of raw materials for the foam and the carbon dioxideadsorbent, by first mixing the polyol, the catalyst, the foamstabilizer, the material containing at least water as a composition forthe blowing agent so as to form a premix. Then, the premix is mixed withthe polyisocyanate and the carbon dioxide adsorbent film-coated by theresin which is permeable to carbon dioxide but hardly permeable to waterthereby manufacturing the foam.

The carbon dioxide adsorbent is produced by soaking an inorganiccompound containing at least one member of an alkali metal hydroxide andan alkaline-earth metal hydroxide with 1 milli-molar equivalent or moreof water based on the total molar amount of the alkali metal hydroxideand the alkaline-earth metal hydroxide in advance.

According to the method for manufacturing the thermal insulating foamedmaterial of the present invention, the carbon dioxide adsorbent waspresent in the raw materials only in a very short duration. Accordingly,even the carbon dioxide adsorbent having a strong catalytic activity isused, a stable foaming can be performed and a thermal insulating foamedmaterial of high quality is obtained without problems such as abnormalreactions.

As mentioned above, since the carbon dioxide adsorbent in the thermalinsulating foamed material has at least one member of the alkali metalhydroxide and the alkaline-earth metal hydroxide and is soaked withwater in advance, the carbon dioxide adsorbent can adsorb and removecarbon dioxide when placed in a carbon dioxide atmosphere, owing to thefacts that the reaction with carbon dioxide proceeds fast by a catalyticaction of water thereby depositing carbonate. Since the carbon dioxideadsorbent is soaked with water in advance, the alkali metal hydroxide orthe alkaline-earth metal hydroxide easily reacts for a long period withcarbon dioxide in the polyurethane thermal insulating foamed materialeven in an air-tight and anhydrous conditions as seen in thepolyurethane thermal insulating foamed material.

Further, since the carbon dioxide adsorbent is uniformly dispersed anddistributed in the thermal insulating foamed material, a distance inwhich carbon dioxide in the cells in the thermal insulating foamedmaterial travels towards the carbon dioxide adsorbent is very short andhence carbon dioxide can be adsorbed and removed within a short time.

In addition, since the carbon dioxide adsorbent is film-coated by aresin, unnecessary urea forming reaction does not occur between thepolyisocyanate and the carrying water of the carbon dioxide adsorbentduring the mixing process of the raw materials.

Still, since carbon dioxide takes some time for passing through theresin of the carbon dioxide adsorbent, the carbon dioxide adsorbent doesnot adsorb carbon dioxide which is acting as a propulsive force forexpanding during foaming. Therefore, no decrease in expansion ratio isresulted in the thermal insulating foamed material having carbon dioxideadsorbents.

Accordingly, the carbon dioxide adsorbent does not adversely affectduring the foaming process after mixing urethane materials but doesadsorb and remove unnecessary carbon dioxide after curing of theurethane resin. By this action, the carbon dioxide in the cells ofurethane resin is removed and hence the thermal insulating foamedmaterial in accordance with the present invention is improved in thermalinsulating ability.

As the volatile blowing agents used in the method for manufacturing thethermal insulating foamed material, can be used hydrocarbon blowingagents such as cyclopentane, n-pentane and the like or hydrofluorocarbonblowing agents such as HFC-356mmf, HFC-245fa and the like.

Further, the thermal insulation cabinet of the present inventioncomprises a box-shaped outer shell as the first wall member, abox-shaped inner shell as the second wall member and the above-mentionedthermal insulating foamed material filled in a space between saidbox-shaped outer shell and said box-shaped inner shell.

In the thermal insulation cabinet, since the carbon dioxide adsorbent isuniformly dispersed in the thermal insulating foamed material, thecarbon dioxide adsorbent has no adverse effect, such as deformation, onthe external appearance of the thermal insulation cabinet. Therefore,the thermal insulation cabinet of the present invention is excellent inthermal insulation properties and of high quality in externalappearance.

As mentioned above, according to the present invention, it is possibleto obtain a thermal insulation material and a thermal insulation cabinetwhich have no problem in mass production and quality and can contributetowards the global environment protection, using the thermal insulatingfoamed material in which a blowing agent mainly comprises carbon dioxidecompletely free from a possibility of causing the ozone depletion andhaving a very little possibility of causing the global warming.

EXAMPLE 1

The thermal insulating foamed material having the carbon dioxideadsorbents, and the thermal insulation cabinet using said thermalinsulating foamed material of Example 1 in accordance with the presentinvention are specifically mentioned below. In the below-mentionedEmbodiments, a foamed rigid polyurethane foam as the thermal insulatingfoamed material is abbreviated as foam.

Table 1 shows the compositions of raw materials for the foam in Example1 and Comparative Examples 1 to 3, and properties of the manufacturedfoam, i.e. density, thermal conductivity and composition of gas incells.

The carbon dioxide adsorbent in Example 1 was produced by coatinggranules of calcium hydroxide and an ion exchanger with apolymethacrylic acid ester.

                                      TABLE 1    __________________________________________________________________________                                Comparative                                      Comparative                                            Comparative                           Ex. 1                                Ex. 1 Ex. 2 Ex. 3    __________________________________________________________________________    Amounts of           Premix                 Polyol    100  100   100   100    raw materials           composition                 Catalyst  3    3     3     3    in parts     Foam stabilizer                           2    2     2     2    by weight    Cyclopentane                           10   10    10    10                 Pure water                           2    2     2     2                 Carbon dioxide                 adsorbent                   Ex. 1 formulation                           10   --    --    --                   Calcium --   --    10    --                   hydroxide alone                   Zeolite --   --    --    10           Polyisocyanate  154  154   154   154    Properties of                 Density (kg/m.sup.3)                           35   34    35    45    polyurethane Thermal conduc-                           0.0147                                0.0160                                      0.0161                                            0.0159    foam         tivity(kcal/mh °C.)                 Composition of                 gas in cells (%)                    Carbon dioxide                            50   75    75    70                   Cyclopentane                           50   25    25    30    __________________________________________________________________________

In Table 1, the polyol was a mixture of an aromatic diamine typepolyetherpolyol and an ethylenediamine type polyetherpolyol having atotal hydroxyl value of 460 mgKOH/g. The foam stabilizer was F-335manufactured by Shin-Etsu Chemical Industry Co., Ltd. (Tokyo). Thecatalyst was KAOLIZER No.31 manufactured by Kao Corporation (Tokyo). Theblowing agent was cyclopentane. The carbon dioxide adsorbents wereproduced by using a reagent of calcium hydroxide having an averageparticle diameter of 50 μm, manufactured by Katayama Kagaku Kogyo Co.,Ltd. (Osaka), as the powders of the alkaline-earth metal hydroxide. Andthe carbon dioxide adsorbents were produced by using an ion exchangeresin SUMIKA-ION KA-890 having an average particle diameter of 100 μm,manufactured by Sumitomo Chemical Co., Ltd. (Osaka), soaked with thesame weight of water as its own weight as the water absorbing powders.The carbon dioxide adsorbent was produced by granulating in a wet spraycoating; the wet spray coating uses a centrifugal rotary fluid bedcoater and granulator manufactured by Freund Industrial Co., Ltd.(Tokyo). Further, using the same apparatus, an organic coatingcomposition containing a methacrylic acid ester as a main ingredient upto an average membrane thickness of 2 μm was formed. These materials, incompounding amounts shown in Table 1, were mixed to a premix.

The wet spray coating is a process in which granules are produced bydispersing a powdery material used as a core in a container, scatteringorganic solution of a resin thereon from a spraying apparatus, in orderto adhere the resin to the core.

Details of 10 parts by weight for the carbon dioxide adsorbent inExample 1 formulation in Table 1 consisted of 6 parts by weight ofcalcium hydroxide, 3 parts by weight of wet ion exchanger and 1 part byweight of the polymethacrylic acid ester.

The polyisocyanate used in Example 1 and Comparative Examples 1 to 3 waspolymeric MDI (diphenylmethane diisocyanate) having an amine equivalentof 135.

The compounded and mixed premix and the polyisocyanate in predeterminedamounts were mixed and agitated. Then they were foamed and filled into aspace formed between the box-shaped inner shell and box-shaped outershell by using of a high pressure foaming machine (temperature of theraw material: 20° C.; discharging pressure: 1.2×10⁷ Pa). As the result,thermal insulation cabinet was obtained.

The thermal insulation cabinet manufactured by the above-mentionedmanner was broken up on the next day and a sample of rigid polyurethanefoam was cut out from the thermal insulating foamed material in thethermal insulation cabinet. And the sample was assayed for density,thermal conductivity and gas composition in the cells at 24 hours afterfoaming. The results are shown in Table 1. The thermal conductivity wasmeasured by means of AUTO-A manufactured by EKO Instruments Trading Co.,Ltd. (Tokyo). The gas composition in the cells was determined by meansof a gas chromatography apparatus manufactured by Shimadzu Corporation(Kyoto).

Further, the results are also shown in Table 1 for experiments in whichno carbon dioxide adsorbent was used (Comparative Example 1), calciumhydroxide alone was used as the carbon dioxide adsorbent (Comparativeexample 2) and zeolite, the conventional adsorbent, was used as thecarbon dioxide adsorbent (Comparative Example 3), for comparisonpurpose.

As is clear in Table 1, the thermal insulating foamed material inExample 1 had much improved thermal insulation properties in thermalconductivity as compared with those in Comparative Examples 1 to 3. Asto the reason, it is considered that a decrease in the amount of carbondioxide is the factor, as is evident from the results of determining gascomposition in the cells. Besides, no decrease in expansion ratio of thefoam was observed for the thermal insulating foamed material in Example1, as is evident from the density of the foam, indicating that noproblem existed in the process of foaming.

On the other hand, in Comparative Example 2, while problem did not existin the process of foaming, the thermal conductivity was high as comparedwith that for the thermal insulating foamed material in Example 1. As tothe reason, it is considered that, after foaming, there is almost nowater was remained in the foam and calcium hydroxide alone could notexert effectively the ability of adsorbing carbon dioxide.

Further, in Comparative Example 3 in which zeolite was used, whilecontent of carbon dioxide was somewhat decreased, no improvement wasnoted in thermal conductivity, and it was revealed that the density ofthe foam was greatly increased. It is considered that zeolite absorbedwater in the raw materials just when it was mixed into the rawmaterials, and water did not act as a blowing agent. This allowedincrease in density of the foam and, together with an adverse effect forsolid thermal conductivity, inhibited improvement in thermalconductivity for the foam.

As mentioned above, the thermal insulating foamed material and thethermal insulation cabinet filled with said thermal insulating foamedmaterial mentioned in Example 1 use granules as a carbon dioxideadsorbent, which is produced by mixing and granulating calcium hydroxidehaving a lower water absorbing property and organic powders having awater absorbing property and soaked with water in advance, and coatingthe surface of the granulated material with a resin. Therefore, thecarbon dioxide adsorbent does not adsorb water in the premix andproblems such as decrease in the expansion ratio of the foam does notexist. Further, since calcium hydroxide is in a state contacting with asubstance soaked with water, it can exert carbon dioxide adsorbingability even in the foam after losing water. Furthermore, since thecarbon dioxide adsorbent in Example 1 is coated by the resin, there isno risk of diffusing water newly generated in the course of the reactionof calcium hydroxide and carbon dioxide.

Accordingly, the thermal insulating foamed material and the thermalinsulation cabinet using said thermal insulating foamed materialmentioned in Example 1 do not adversely affect the properties of thefoam and the carbon dioxide in the cells of the foam is removed allowingimprovement of the thermal insulating property of the foam.

As mentioned above, the thermal insulating foamed material and thethermal insulation cabinet using said thermal insulating foamed materialmentioned in Example 1 are of high quality with a high thermalinsulating ability and without any problem for properties of the foamutilizing cyclopentane, which is one of hydrocarbons completely freefrom an ozone depletion and almost no effect to the global warming; andhence they are essential for the protection of global environment as theblowing agent for polyurethane foam.

While calcium hydroxide was used as a carbon dioxide adsorbent inExample 1, any powders of alkali metal hydroxide or alkaline-earth metalhydroxide, such as potassium hydroxide and the like, can be used withthe same effects as Example 1. Further, while an ion exchange resin wasused as the water carrying substance in Example 1, any water absorbingmaterial, irrespective of organic or inorganic, can be used with thesame effects as those in Example 1.

Besides, the same effects as those in Example 1 can also be obtainedusing a carbon dioxide adsorbent produced by granulating powders of analkali metal hydroxide or an alkaline-earth metal hydroxide using anorganic or inorganic substance containing water as a binder, and coatingthe surface of the granulated material with a resin which is permeableto carbon dioxide but hardly permeable to water. Furthermore, in suchExample used organic or inorganic as a binder, since the step forhumidifying the water carrying substance and the step for mixing withthe powders of an alkali metal hydroxide or the like in Example 1 becomeunnecessary, there may be an advantage that the costs for productioncould be lowered.

The thermal insulating foamed material having the carbon dioxideadsorbents mentioned in Example 1 has an advantage that carbon dioxideis removed by the carbon dioxide adsorbent and without adverse effect tothe expansion ratio of the foam, because the carbon dioxide adsorbentnever adsorb water in the materials for the foam.

EXAMPLE 2

A thermal insulating foamed material having carbon dioxide adsorbents,and a thermal insulation cabinet using said thermal insulating foamedmaterial of Example 2 in accordance with the present invention arespecifically mentioned below referring to FIG. 1 and FIG. 2.

FIG. 1 shows a schematic view of a carbon dioxide adsorbent mentioned inExample 2. FIG. 2 shows a sectional view of a thermal insulation cabinetmentioned in Example 2.

The carbon dioxide adsorbent 8 shown in FIG. 1 has a composition inwhich an alkaline-earth metal hydroxide 1 and a hydrate 2 of inorganiccompound having a heat of hydration of 20 kcal/mol or more are finelygranulated and then are formed to granules of desired sizes using aresin 3 as a binder and the surface of the granulated materials iscoated. The carbon dioxide in the cells of the thermal insulating foamedmaterial permeates through the resin 3, and is dissolved in the hydrate2 of inorganic compound. And further, the carbon dioxide has reactionsto the alkaline-earth metal hydroxide 1 thereby fixing carbon dioxide.

The thermal insulation cabinet 9 shown in FIG. 2 is manufactured byfilling thermal insulating foamed material 7 in the space 6 between thebox-shaped inner shell 4 and box-shaped outer shell 5. The thermalinsulating foamed material 7 has the carbon dioxide adsorbent 8dispersed therein.

Table 2 shows the compositions of the raw materials for the foam inExample 2 and Comparative Examples 4 to 6, and properties of themanufactured foam, i.e. density, thermal conductivity and composition ofgas in cells.

The carbon dioxide adsorbent in Example 2 was produced by coatingaggregated granules of calcium hydroxide and magnesium chloridehexahydrate with polymethacrylic acid ester.

                                      TABLE 2    __________________________________________________________________________                                Comparative                                      Comparative                                            Comparative                           Ex. 2                                Ex. 4 Ex. 5 Ex. 6    __________________________________________________________________________    Amounts of           Premix                 Polyol    100  100   100   100    raw materials           composition                 Catalyst  3    3     3     3    in parts     Foam stabilizer                           2    2     2     2    by weight    Cyclopentane                           10   10    10    10                 Pure water                           2    2     2     2                 Carbon dioxide                 adsorbent                   Ex. 2 formulation                           10   --    --    --                   Calcium --   --    10    --                   hydroxide alone                   Zeolite --   --    --    10           Polyisocyanate  154  154   154   154    Properties of                 Density (kg/m.sup.3)                           35   34    35    45    polyurethane Thermal conduc-                           0.0147                                0.0160                                      0.0161                                            0.0159    foam         tivity(kcal/mh °C.)                 Composition of                 gas in cells (%)                    Carbon dioxide                            50   75    75    70                   Cyclopentane                           50   25    25    30    __________________________________________________________________________

the catalyst and the blowing agent, the same raw materials as theaforementioned materials in Example 1 were used.

The carbon dioxide adsorbent 8 were produced by using a reagent ofcalcium hydroxide having an average particle diameter of 50 μm,manufactured by Katayama Kagaku Kogyo Co., Ltd., as the powders of thealkaline-earth metal hydroxide and magnesium chloride hexahydrate havinga heat of hydration of 33.11 kcal/mol manufactured by Wako Pure ChemicalIndustries Ltd. as a metal hydrate. The carbon dioxide adsorbent 8 wasproduced by granulating in wet spray coating; the wet spray coating usesthe centrifugal rotary fluid bed coater and granulator manufactured byFreund Industrial Co., Ltd. and a resin mainly consisting of methacrylicacid ester as a binder. Further, using the same apparatus, afilm-coating having an average membrane thickness of 2 μm was formed.

These materials mentioned above, in compounding amounts shown in Table2, were mixed to a premix.

Details of 10 parts by weight for the carbon dioxide adsorbent 8 inExample 2 formulation in Table 2 consisted of 6 parts by weight ofcalcium hydroxide, 3 parts by weight of magnesium chloride hydrate and 1part by weight of the polymethacrylic acid ester.

The polyisocyanate used in Example 2 and Comparative Examples 4 to 6 waspolymeric MDI having an amine equivalent of 135.

The compounded and mixed premix and the polyisocyanate in predeterminedamounts were mixed and agitated. Then they were foamed and filled intothe space 6 formed between the box-shaped inner shell 4 and box-shapedouter shell 5 by using of a high pressure foaming machine (temperatureof the raw material: 20° C.; discharging pressure: 1.2×10⁷ Pa). As theresult, the thermal insulation cabinet 9 of Example 2 was obtained.

The thermal insulation cabinet manufactured by the above-mentionedmanner was broken up on the next day and a sample of rigid polyurethanefoam was cut out from the thermal insulating foamed material 7 in thethermal insulation cabinet 9. And the sample was assayed for density,thermal conductivity and gas composition in the cells at 24 hours afterfoaming. The results are shown in Table 2. The thermal conductivity wasmeasured by means of AUTO-A manufactured by EKO Instruments Trading Co.,Ltd. The gas composition in the cells was determined by means of a gaschromatography apparatus manufactured by Shimadzu Corporation.

Further, the results are also shown in Table 2 for experiments in whichno carbon dioxide adsorbent was used (Comparative Example 4), calciumhydroxide alone was used as the carbon dioxide adsorbent (Comparativeexample 5) and zeolite, the conventional adsorbent, was used as thecarbon dioxide adsorbent (Comparative Example 6), for comparisonpurpose.

As is clear in Table 2, the thermal insulating foamed material inExample 2 had a much improved thermal conductivity as compared withthose in Comparative Examples 4 to 6. As to the reason, it is consideredthat a decrease in the amount of carbon dioxide is the factor, as isevident from the results of determining gas composition in the cells.Besides, no decrease in expansion ratio of foam was observed for thethermal insulating foamed material in Example 2 in comparison with eachComparative Example, as is evident from the density of the foam,indicating that no problem existed in the process of foaming.

On the other hand, the product in Comparative Example 5 had the samedensity as that in Example 2, as shown in the density of the foam inTable 3, and no problem existed in the process of foaming. However, thethermal conductivity of the product in Comparative Example 5 was high incomparison with that in Example 2. As to the reason, it is consideredthat, after foaming, there is almost no water was remained in the foamand calcium hydroxide could not exert effectively the ability ofadsorbing carbon dioxide.

Further, in Comparative Example 6 in which zeolite was used, whilecontent of carbon dioxide was somewhat decreased, no improvement wasnoted in thermal conductivity, and it was revealed that the density wasgreatly increased. As to the reason, it is considered that zeoliteabsorbed water in the raw materials just when it was mixed into the rawmaterials and therefore water did not act as a blowing agent. Thisallowed increase in density of the foam and, together with an adverseeffect for solid thermal conductivity, inhibited improvement in thermalconductivity for the foam.

As mentioned above, the carbon dioxide adsorbent in Example 2 producedby mixing and forming to granules of calcium hydroxide and magnesiumchloride hexahydrate followed by coating the surface of the granulatedmaterial with a resin, which is permeable to carbon dioxide but hardlypermeable to water. Therefore, it is possible to granulate withoutvaporizing water in the hydrate. In addition, by using such carbondioxide adsorbent in the thermal insulating foamed material, the carbondioxide adsorbent does not adsorb water in the premix and problems suchas decrease in the expansion ratio of the foam does not exist. Further,since calcium hydroxide in the carbon dioxide adsorbent is in a statecontacting with a substance soaked with water, it can exert carbondioxide adsorbing ability even in the foam after losing water.Furthermore, since the carbon dioxide adsorbent is coated by the resin,there is no risk of diffusing water newly generated in the course of thereaction of calcium hydroxide and magnesium chloride with carbondioxide.

While calcium hydroxide was used as a carbon dioxide adsorbent inExample 2, any powders of alkali metal hydroxide or alkaline-earth metalhydroxide, such as potassium hydroxide and the like, can be used withthe same effects as those in Example 2. Further, while magnesiumchloride hexahydrate was used as the hydrate of inorganic compound inExample 2, other inorganic or metal hydroxides such as barium hydroxideoctahydrate, sodium carbonate decahydrate and the like, preferably aninorganic or metal hydrate having a heat of hydration of 20 kcal/mol ormore, can be used with the same effects as those in Example 2.

EXAMPLE 3

A thermal insulating foamed material having carbon dioxide adsorbents,and a thermal insulation cabinet using the thermal insulating foamedmaterial of Example 3 in accordance with the present invention arespecifically mentioned below referring to FIG. 3 to FIG. 5.

FIG. 3 shows a sectional view, partly cut away, of the thermalinsulation cabinet mentioned in Example 3. FIG. 4 shows a sectional viewof the thermal insulation cabinet mentioned in Example 3 directly beforefilling raw materials. FIG. 5 shows a sectional view of the thermalinsulation cabinet mentioned in Example 3 after filling the rawmaterials.

In FIG. 3, the thermal insulation cabinet 90 has a box-shaped outershell 50 as the first wall member, a box-shaped inner shell 40 as thesecond wall member and a thermal insulating foamed material 70 filled inthe space 60 between the box-shaped inner shell 40 and box-shaped outershell 50. The thermal insulating foamed material 70 has the carbondioxide adsorbents 80 dispersed therein.

Further, the thermal insulation cabinet 90 in accordance with Example 3is produced by filling the thermal insulating foamed materials in thespace 60 between the box-shaped outer shell 50 as the first wall memberand the box-shaped inner shell 40 as the second wall member. Then thepolyol, the catalyst, the foam stabilizer, the material containing atleast water as a composition for the blowing agent, said carbon dioxideadsorbent 80 coated by the resin and the polyisocyanate are mixed andagitated, and filled in the space 60, in order to produce the thermalinsulating foamed material 70 by foaming.

Table 3 shows the compositions of the raw materials for the foam inExample 3 and Comparative Examples 7 and 8, and properties of themanufactured foam, i.e. density, thermal conductivity and composition ofgas in cells.

The carbon dioxide adsorbents in Example 3 were produced by coatinggranules of calcium hydroxide with a polyvinyl acetate resin aftersoaking with 0.01 molar equivalent of water.

                                      TABLE 3    __________________________________________________________________________                                Comparative                                      Comparative                           Ex. 3                                Ex. 7 Ex. 8    __________________________________________________________________________    Amounts of           Premix                 Polyol    100  100   100    raw materials           composition                 Catalyst  3    3     3    in parts     Foam stabilizer                           2    2     2    by weight    Cyclopentane                           8    8     8                 Pure water                           2    2     2                 Carbon dioxide                 adsorbent                   Ex. 3 formulation                           30   --    --                   Absorbent with-                           --   --    10                   out soaking water           Polyisocyanate  154  154   154    Properties of                 Density (kg/m.sup.3)                           39   39    35    polyurethane Thermal conduc-                           0.0145                                0.0162                                      0.0162    foam         tivity(kcal/mh °C.)                 Composition of                 gas in cells (%)                    Carbon dioxide                            50   75    75                   Cyclopentane                           50   25    25    __________________________________________________________________________

In the premix, the polyol was a polyetherpolyol, having a hydroxyl valueof 460 mgKOH/g, produced by addition polymerization of an aromaticdiamine with an alkylene diamine as an extender. The catalyst forpromoting a reaction of the polyol and the isocyanate was KAOLIZER No.1(N,N,N',N'- tetramethyl hexamethylenediamine) manufactured by KaoCorporation. The foam stabilizer was F-337, a silicone foam stabilizer,manufactured by Shin-Etsu Chemical Industry Co., Ltd.. The blowing agentwas cyclopentane and water. They were mixed in a composition shown inTable 3.

Details of 30 parts by weight for the carbon dioxide adsorbent 80 inExample 3 formulation in Table 3 consisted of 27 parts by weight ofcalcium hydroxide, 3 parts by weight of polyvinyl acetate.

The carbon dioxide adsorbent 80 in Example 3 was produced by soakingcalcium hydroxide with 0.01 molar equivalent of water and then applyinga film-coating of polyvinyl acetate in the wet spray coating process.

The polyisocyanate used in Example 3 and Comparative Examples 7 and 8was polymeric MDI (diphenylmethane diisocyanate) having an amineequivalent of 135.

Immediately before filling raw materials to the thermal insulationcabinet 90 shown in FIG. 4, a mixture is prepared by mixing andagitating the premix and the polyisocyanate in predetermined amounts bymeans of a high pressure foaming machine (not shown). The mixture isfilled from discharge heads 20 into a space 60 formed between thebox-shaped inner shell 40 and box-shaped outer shell 50 through inlets100 for filling. In a flange 110 of the cabinet under the inlets 100 forfilling, granules of the carbon dioxide adsorbent 80 are placed inadvance.

The materials discharged from the discharge heads 20 is filled into thespace 60 catching the carbon dioxide adsorbent 80 and uniformly mixing.The polyurethane foam, which is the thermal insulating foamed material70 as filled, is hardened as the time proceeds, upon which the thermalinsulation cabinet 90 was obtained.

The thermal insulation cabinet 90 thus obtained was of high qualitywithout problems in external appearance such as deformation or the like.The thermal insulation cabinet 90 was broken up on the next day and asample of the rigid polyurethane foam was taken. The sample of the rigidpolyurethane foam was assayed for density of the foam, thermalconductivity of the foam and gas composition in the cells at 24 hoursafter foaming. The results are shown in Table 3.

In Table 3, results are also shown for density, thermal conductivity andgas composition in cells measured for a rigid polyurethane foam formedusing a carbon dioxide adsorbent produced by film-coating calciumhydroxide without soaking water, as Comparative Example 7.

Further, the results are also shown in Table 3 for density, thermalconductivity and as composition in cells for a rigid polyurethane foamformed without using carbon dioxide adsorbent, as Comparative Example 8.

As is clear in Table 3, the thermal insulating foamed material 70 inExample 3 had a much decreased ratio of carbon dioxide in the gascomposition in the cells and an improvement by about 10% in thermalconductivity of the rigid polyurethane foam as compared with those inComparative Examples 8 in which no carbon dioxide adsorbent was added.

Also, in Comparative Example 7 in which the polyurethane foam was formedusing a carbon dioxide adsorbent film-coated with the polyvinyl acetateresin without soaking with water, neither decrease in ratio of carbondioxide nor improvement in thermal conductivity of the foam wasobserved.

While calcium hydroxide was used as the carbon dioxide adsorbent inabove Example 3, the same effects as those in Example 3 can be obtainedby using potassium hydroxide, sodium hydroxide, barium hydroxide or amixture thereof. Further, it is also possible to use a carbon dioxideadsorbent produced by film-coating an oxide such as calcium oxide with aresin composition after soaking with more than 1 milli-molar equivalentof water.

As a resin composition for film-coating, an acrylic resin, a urethaneresin and the like can be utilized in a manner similar to the vinylresin.

As mentioned above, the thermal insulation cabinet having with thethermal insulating foamed material in Example 3 is extremely useful as acabinet for a refrigerator or a freezer and can impart a quality as anexcellent thermal insulation cabinet.

Although the present invention has been mentioned in terms of thepresently preferred embodiments, it is to be understood that suchdisclosure is not to be interpreted as limiting. Various alterations andmodifications will no doubt become apparent to those skilled in the artto which the present invention pertains, after having read the abovedisclosure. Accordingly, it is intended that the appended claims beinterpreted as covering all alterations and modifications as fall withinthe true spirit and scope of the invention.

What is claimed is:
 1. A thermal insulating foamed material, whichcomprises a foamed polyurethane resin composition having closed cells,which has therein carbon dioxide adsorbents formed by at least onemember of carbonates of alkali metal and carbonates of alkaline-earthmetal, covered with resin coating, and has volatile blowing agent insaid closed cells.
 2. A thermal insulating foamed material in accordancewith claim 1, wherein said carbon dioxide adsorbent has at least onemember of hydroxides of alkali metal and hydroxides of alkaline-earthmetal forming a mixture with said carbonates of alkali metal or saidcarbonate of alkaline-earth metal.
 3. A thermal insulating foamedmaterial in accordance with claim 1, wherein said carbon dioxideadsorbent contains water within said resin coating.
 4. A thermalinsulating foamed material in accordance with claim 1, wherein saidcarbon dioxide adsorbent is formed with a coating resin film, which ispermeable to carbon dioxide but hardly permeable to water.
 5. A thermalinsulating foamed material in accordance with claim 1, wherein saidcarbon dioxide adsorbent is formed with a coating resin film consistingof at least one member selected from the group consisting of polyvinylalcohol, polyvinyl acetate, polyvinyl pyrrolidone, polyacrylic acidester, polymethacrylic acid ester, ethyl cellulose, and carboxymethylethyl cellulose.
 6. A thermal insulating foamed material in accordancewith claim 1, wherein said carbon dioxide adsorbent has an outerdimension of from 0.2 mm to 1.0 mm.
 7. A thermal insulation cabinetcomprising:a first wall member, a second wall member and a foamedpolyurethane resin composition which is filled in a space formed betweensaid first wall member and said second wall member, has therein carbondioxide adsorbents formed by at least one member of carbonates of alkalimetal and carbonates of alkaline-earth metal, covered with resincoating, and has volatile blowing agent in closed cells of said foamedpolyurethane resin composition.
 8. A thermal insulation cabinet inaccordance with claim 7, wherein said carbon dioxide adsorbent furthercontains at least one member of hydroxides of alkali metal andhydroxides of alkaline-earth metal forming a mixture with saidcarbonates of alkali metal or said carbonates of alkaline-earth metal.9. A thermal insulation cabinet in accordance with claim 7, wherein saidcarbon dioxide adsorbent contains water within said resin coating.
 10. Athermal insulation cabinet in accordance with claim 7, wherein saidcarbon dioxide adsorbent is formed with a coating resin film, which ispermeable to carbon dioxide but hardly permeable to water.
 11. A thermalinsulation cabinet in accordance with claim 7, wherein said carbondioxide adsorbent is formed with a coating resin film of at least onemember selected from the group consisting of polyvinyl alcohol,polyvinyl acetate, polyvinyl pyrrolidone, polyacrylic acid ester,polymethacrylic acid ester, ethyl cellulose, and carboxymethyl ethylcellulose.
 12. A thermal insulation cabinet in accordance with claim 7,wherein said carbon dioxide adsorbent has an outer dimension of from 0.2mm to 1.0 mm.
 13. A thermal insulating foamed material in accordancewith claim 2, wherein said carbon dioxide adsorbent contains waterwithin said resin coating.
 14. A thermal insulating foamed material inaccordance with claim 2, wherein said carbon dioxide adsorbent is formedwith a coating resin film, which is permeable to carbon dioxide buthardly permeable to water.
 15. A thermal insulating foamed material inaccordance with claim 2, wherein said carbon dioxide adsorbent is formedwith a coating resin film consisting of at least one member selectedfrom the group consisting of polyvinyl alcohol, polyvinyl acetate,polyvinyl pyrrolidone, polyacrylic acid ester, polymethyacrylic acidester, ethyl cellulose, and carboxymethyl ethyl cellulose.
 16. A thermalinsulating foamed material in accordance with claim 2, wherein saidcarbon dioxide adsorbent has an outer dimension of from 0.2 mm to 1.0mm.
 17. A thermal insulation cabinet in accordance with claim 8, whereinsaid carbon dioxide adsorbent contains water within said resin coating.18. A thermal insulation cabinet in accordance with claim 8, whereinsaid carbon dioxide adsorbent is formed with a coating resin film, whichis permeable to carbon dioxide but hardly permeable to water.
 19. Athermal insulation cabinet in accordance with claim 8, wherein saidcarbon dioxide adsorbent is formed with a coating resin film of at leastone member selected from the group consisting of polyvinyl alcohol,polyvinyl acetate, polyvinyl pyrrolidone, polyacrylic acid ester,polymethacrylic acid ester, ethyl cellulose, and carboxymethyl ethylcellulose.
 20. A thermal insulation cabinet in accordance with claim 8,wherein said carbon dioxide adsorbent has an outer dimension of from 0.2mm to 1.0 mm.